1. Field of the Invention
The present invention relates to an inkjet recording apparatus and an inkjet recording method, and more particularly, to an inkjet recording apparatus and an inkjet recording method using a reaction of two liquids, in which recording is performed by ejecting a first liquid which contains a solvent-insoluble material, and a second liquid which causes the solvent-insoluble material to aggregate, from respectively different ejection ports.
2. Description of the Related Art
There is a recording apparatus using an inkjet recording method (i.e., an inkjet recording apparatus), which performs recording by ejecting ink droplets to a recording medium from a plurality of nozzles (ejection ports), which are arranged on an ejection surface of a recording head. This kind of apparatus is used widely in both domestic and industrial applications, due to its low noise, low running costs, and the fact that it allows compact design. In a recording apparatus of this kind, if a recording medium having low water-resistance is used, such as normal paper, then color bleeding, feathering, density insufficiencies, and the like, are liable to occur, and a good image cannot be obtained, since it is not possible to set the density of the coloring material contained in the ink to a very high level, in order to achieve stable ejection over a long period of time.
One means for improving image quality in an inkjet recording apparatus is to use special paper (e.g., special inkjet paper) that has an ink absorbent layer. However, if special paper is used, then costs rise, placing a greater burden on the user, and since the thickness of the paper is increased in accordance with the thickness of the ink absorbent layer, then the aesthetic properties of the paper are also different to normal paper, and therefore special paper is not a desirable solution for all users.
There is an inkjet recording apparatus using a two-liquid reaction system, in which an ink and a treatment liquid are ejected from different ejection ports (nozzles), respectively. The ink contain& a coloring material, and the treatment liquid causes the coloring material to become insoluble or to aggregate By causing the ink and the treatment liquid to react with each other on the recording medium, the coloring material is insolubilized or caused to aggregate, thereby raising the fixing properties of the image, and satisfactory image quality that is free of color bleeding or feathering can be obtained. For example, Japanese Patent Application Publication No. 01-063185 discloses that a colorless ink (corresponding to a treatment liquid) that insolubilizes a dye is deposited onto a recording medium by a recording head. Japanese Patent Application Publication No. 05-202328 discloses that a polyvalent metal salt solution (corresponding to a treatment liquid) is first deposited on a recording medium, and then an ink containing a chemical dye having a carboxyl group is deposited thereon, in order to obtain images having good waterproofing characteristics and free of color bleeding. Japanese Patent Application Publication No. 2003-034070 discloses that an ink in which cationic resin micro-particles and organic pigment are combined and a recording characteristics enhancing liquid (corresponding to a treatment liquid) are used to achieve better lightfastness.
In the inkjet recording apparatus, ink contamination on the ejection surface of the recording head is a relatively common phenomenon. The ink contamination is caused by, for example: the adherence of satellite droplets of the ink, which are generated during ink ejection, to the ejection surface; the adherence of the ink to the ejection surface during maintenance operations, such as the nozzle suction or wiping; and the adherence of the ink on the recording medium to the ejection surface caused by the recording medium making contact with the ejection surface during conveyance. In a general inkjet recording apparatus other than the inkjet recording apparatus using the two-liquid reaction system, it is possible to remove the ink contamination on the ejection surface by carrying out preliminary ejection, nozzle suction, wiping, or the like; however, in the inkjet recording apparatus using the two-liquid reaction system, the ink contamination is a particularly serious problem. The treatment liquid is used with the object of making react with the ink on the recording medium, and if there is ink contamination on the ejection surface, then unwanted reaction occurs such that the openings of the nozzles become partially or completely blocked up by insolubilized or aggregated coloring material, which can readily lead to ejection defects, such as ejection failure.
Japanese Patent Application Publication No. 08-281968 discloses an inkjet printer having a plurality of wiping members and restricting the direction of wiping so as to prevent unwanted reaction, in order to ensure the reliability of the apparatus.
Furthermore, there is also technology which uses a set of a reactive ink and a cleaning agent that suppresses reaction of the ink, wherein a method for cleaning the recording head with the cleaning liquid is adopted and countermeasures are carried out once the recording head has ceased to be able to perform ejection due to the occurrence of unwanted reaction (see, for example, Japanese Patent Application Publication Nos. 2004-098684 and 2004-115553). Moreover, there is also technology in which a cleaning agent is applied to the ejection surface before ink ejection so that countermeasures are carried out proactively in order to prevent unwanted reaction of the ink (see, for example, Japanese Patent Application Publication No. 2005-254599).
On the other hand, there are also methods which improve the functionality of the ink by adding a resin component to the ink. A typical example for improving the functionality is a method in which a fixing resin is added to an ink, more specifically, an ink with added polymer latex is used, and when this ink is heated to a temperature equal to or greater than the glass transition temperature of the polymer latex after depositing this ink on the recording medium, the fixing properties and wear resistance of the image on the recording medium are improved, and furthermore, luster and a sense of transparency are imparted to the resulting Image (see, for example, Japanese Patent Application Publication Nos. 2000-085238 and 2003-171588).
However, in Japanese Patent Application Publication No. 08-281968, even if it is possible to prevent unwanted reaction to some extent, no countermeasures are provided in respect of reacted material that has already solidified. In particular, when using a pigment ink, aggregate of the pigment becomes fixed to the ejection surface due to the reaction with the treatment liquid, and it becomes impossible to restore the ejection surface to its original state, therefore leading, in the worst scenario, to a risk of serious damage to the recording head.
Moreover, in Japanese Patent Application Publication Nos. 2004-098684, 2004-115553 and 2005-254599, if the number of ink types is increased in order to improve color reproduction, then it is known that even if the same cleaning agent is used, a phenomenon of differing dispersion characteristics of the inks arises, and therefore a sufficient cleaning effect cannot be achieved.
Furthermore, in Japanese Patent Application Publication Nos. 2000-085238 and 2003-171588, although it is possible to achieve image recording which is free of bleeding, by using an ink containing resin additive, it is known that if the latex performs an unwanted reaction, then material that normally does not fuse unless heated to the glass transition temperature or above does fuse at a relatively low temperature, and the resin component becomes affixed solidly to the recording head, thus giving rise to ejection defects. Moreover, it is known that even if the recording head is cleaned by using the cleaning liquid in this state, the recording head cannot be restored and critical problems arise.